The present invention relates to a disc drive storage system. In particular, the present invention relates to an improved gimbal suspension which supports a disc head slider at its leading edge.
Disc drives of the "Winchester" type are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a preload force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc. It is important that the gimbal be designed to withstand and distribute flexure forces so that the suspension system does not fail due to fatigue.
The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air under the slider along the air bearing surfaces in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the air bearing surface, skin friction on the air bearing surface causes the air pressure between the disc and the air bearing surface to increase which creates a hydrodynamic lifting force that causes the slider to lift and fly above the disc surface. The preload force supplied by the load beam counteracts the hydrodynamic lifting force. The preload force and the hydrodynamic lifting force reach an equilibrium based upon the hydrodynamic properties of the slider and the speed of rotation of the disc.
The slider preferably flies with a positive pitch in which the leading edge of the slider flies at a greater distance from the disc surface than the trailing edge. This ensures that the transducer, which is typically carried at the trailing edge, remains close to the disc surface and provides a stable fly height profile across the disc surface. Tolerance variations during attachment of the slider to the gimbal relative to the location of the preload force can alter the pitch angle of the slider as well as the alignment characteristics of the slider. It is desirable to provide a gimbal which facilitates the attachment of a slider to the gimbal to produce a head gimbal assembly having the desired pitch characteristics as well as alignment characteristics.
In addition, accurate positioning of the transducer relative to the data tracks is important for accurate, reliable recording. As the track spacing or track "pitch" continues to decrease in modern disc drives, it becomes increasingly difficult for traditional actuators to accurately position a transducer over the ideal center of a desired data track. As a result, microactuation devices have been proposed to improve the ability of the actuator system to finely position a transducer over the ideal track center.
Another difficulty in positioning the transducer arises with the use of magnetoresistive ("MR") heads. In an MR head, there is an offset between the active magnetic centers of the read transducer and write transducer on a single MR head. Because of mask misalignment during manufacture, the read and write transducers can be spatially separated from one another to a greater or lesser degree than otherwise desired. Thus, when the MR head is finally positioned over a track during a write operation, that same position is not the ideal track center for the MR head during the read operation. Since the read transducer is spatially separated from the write transducer, the MR head must be radially moved within the track, or repositioned within the track, so that the read transducer position is over the ideal track center.
The problem of spatial separation is further complicated because the skew angle (the angle of the MR head with respect to a track on a disc surface) changes in different zones on the disc surface. Thus, the effective spatial separation in the read and write transducers on the MR head also changes across the disc surface.
Thus, it is desirable to provide a suspension system which can facilitate microactuation control of the slider about the yaw axis to finely position the read and write transducers over the ideal track centers and to compensate for skew angle.